Ohmic electrode structure and semiconductor element

Abstract

The present invention includes an AuGeNi alloy layer ( 13 ) provided on an n-type GaAs layer; and a laminate provided on the AuGeNi alloy layer ( 13 ), the laminate being composed of a bonding metal layer ( 15, 17 ) and a barrier metal layer ( 16, 18 ) provided on the bonding metal layer ( 15, 17 ). The present invention includes two or more of the laminates. With this configuration, in a GaAs-based contact layer, particularly in an n-type electrode, the surface diffusion of Ga of the semiconductor and Ni of the AuGeNi alloy, which is needed to form an ohmic contact in the n-type electrode, can be suppressed, and a low-resistance ohmic electrode structure and a semiconductor element having the ohmic electrode structure can be provided.

1 . An ohmic electrode structure comprising:
 an AuGeNi alloy layer provided on an n-type GaAs layer; and   a laminate provided on the AuGeNi alloy layer, the laminate being composed of a bonding metal layer and a barrier metal layer provided on the bonding metal layer,   wherein the ohmic electrode structure includes two or more of the laminates.   
   
   
       2 . The ohmic electrode structure according to  claim 1 ,
 wherein the barrier metal layer is made of Pt or Pd, and   the bonding metal layer is made of Ti or Ni.   
   
   
       3 . The ohmic electrode structure according to  claim 1 ,
 wherein the laminate on the AuGeNi alloy layer is a first laminate,
 the bonding metal layer of the first laminate has a thickness of 100 nm or more, and 
 the barrier metal layer of the first laminate is thinner than the bonding metal layer of the first laminate. 
   
   
   
       4 . The ohmic electrode structure according to  claim 3 , wherein the thickness of the barrier metal layer of the first laminate is ½ or less of that of the bonding metal layer of the first laminate. 
   
   
       5 . The ohmic electrode structure according to  claim 1 ,
 wherein the laminate on the AuGeNi alloy layer is a first laminate,   assuming that the number of the laminates is ‘a’, the barrier metal layer of the a-th laminate has a thickness of 100 nm or more, and   the bonding metal layer of the a-th laminate is thinner than the barrier metal layer of the a-th laminate.   
   
   
       6 . The ohmic electrode structure according to  claim 5 , wherein the thickness of the bonding metal layer of the a-th laminate is ½ or less of that of the barrier metal layer of the a-th laminate. 
   
   
       7 . The ohmic electrode structure according to  claim 5 , wherein assuming that the number of the laminates is 3 or more, each of the bonding metal layers and each of the barrier metal layers interposed between the first laminate and the a-th laminate are thinner than the bonding metal layer of the first laminate and the barrier metal layer of the a-th laminate, respectively. 
   
   
       8 . The ohmic electrode structure according to  claim 1  further comprising an Au layer predominantly composed of Au on top of the laminates,
 wherein the Au layer has a film thickness of 100 nm or more.   
   
   
       9 . A semiconductor element comprising the ohmic electrode structure according to  claim 1 ,
 wherein a semiconductor layer including the n-type GaAs layer has a film thickness of 80 μm or more and 120 μm or less.   
   
   
       10 . The semiconductor element according to  claim 9 , further comprising a second electrode structure, the second electrode structure being provided on a back side of the semiconductor element with respect to a side on which the ohmic electrode structure is provided. 
   
   
       11 . The semiconductor element according to  claim 10 , wherein the second electrode structure includes at least one of Au, Pt and Ti. 
   
   
       12 . The semiconductor element according to  claim 10 , wherein the second electrode structure includes an Au layer predominantly composed of Au as an uppermost layer thereof, and the Au layer of the second electrode structure has a film thickness of 100 nm or more. 
   
   
       13 . A semiconductor device comprising a plurality of the semiconductor elements according to  claim 9 , each of the semiconductor elements being provided with the ohmic electrode structure,
 wherein the ohmic electrode structures are separated by a boundary region between the semiconductor elements.   
   
   
       14 . A semiconductor device comprising a plurality of the semiconductor elements according to  claim 10 , each of the semiconductor elements including a plurality of the second electrode structures,
 wherein the second electrode structures are separated by a boundary region between the semiconductor elements.   
   
   
       15 . The semiconductor element according to  claim 10 ,
 wherein a bonding metal material in the ohmic electrode structure and a bonding metal material in the second electrode structure are made of the same element, and a barrier metal material in the ohmic electrode structure and a barrier metal material in the second electrode structure are made of the same element, and   a sum of film thicknesses of the layers of the bonding metal material in the ohmic electrode structure and that in the second electrode structure are equal to each other, and a sum of film thicknesses of the layers of the barrier metal material in the ohmic electrode structure and that in the second electrode structure are equal to each other.   
   
   
       16 . The semiconductor element according to  claim 10 ,
 wherein a bonding metal material in the ohmic electrode structure and a bonding metal material in the second electrode structure are made of the same element, and a barrier metal material in the ohmic electrode structure and a barrier metal material in the second electrode structure are made of the same element,   the second electrode structure includes a laminate in which the bonding metal material and the barrier metal material are laminated, and   a sum of film thicknesses of the layers of the bonding metal material in the ohmic electrode structure and that in the second electrode structure are equal to each other, and a sum of film thicknesses of the layers of the barrier metal material in the ohmic electrode structure and that in the second electrode structure are equal to each other.